The game of chess 1 (Prior Art FIG. 1), premised on the experience of war and conflict, dates back to India in the 6th century during the Gupta empire, and today it is played world-wide according to rules maintained by the World Chess Federation. It is a two-player game. The square board 2 on which it is played consists of 64 squares arranged in an eight-by-eight grid of rows 3 (called “ranks”) and columns 4 (known as “files”). Ranks are identified by the numbers 1 to 8 and columns by the letters A to H. The squares alternate between black and white. Each player starts with 16 pieces 5, white for one player, black for the other. The pieces include a king 6, a queen 7, two rooks (or castles) 8, two bishops 9, two knights 10, and eight pawns 11. Each piece moves in its own unique fashion.
In traditional chess, the object of the game is to remove the pieces controlled by one's opponent and maneuver the opposing king into checkmate. During the course of game play special moves are possible such as castling, en passant, and promotion of a chess piece. Today there are many variations on the traditional game of Western chess.
For example, U.S. Pat. No. 6,000,698 to Woodward proposed a form of chess in which captured pieces can be used by the captor. In the game described in this patent, the rules of Western chess and Shogi are combined with an entirely new chess piece design involving an upright stem with a shape denoting the piece's denomination and a direction indicator that identifies the ownership of the piece.
Shogi, often called Japanese chess, dates back to the 16th century. The game is played with 20 flat, wedge-shaped pieces not differing in color on a board of 9 rows and 9 columns. Pieces in Shogi, which differ in size, are marked on their surface with Chinese characters, have other markings on their reverse side, and can be promoted when a piece is turned over. Promotion occurs when a piece reaches the three ranks (or promotion zone) on the far side where the opponent's pieces were set up at the start of the game. The pieces for each player include one king, one rook, one bishop, two gold generals, two silver generals, two knights, two lances, and nine pawns. Ownership of the piece is determined by the direction toward which the piece is pointing, that is, the smaller end points toward one's opponent.
What distinguishes Shogi is its “drop rule,” which allows players to return to the board pieces captured from an opponent and use them as one's own. Once captured, a piece may be held “in hand” on a wooden stand at the bottom right corner of the board, then returned to play anywhere on the board. Each drop counts as a move by the player. But a drop cannot capture an opponent's piece. And a drop in the promotion zone does not lead to immediate promotion. Two restrictions must not be violated. First, a pawn cannot be placed on the same column as another unpromoted pawn; and, secondly, a pawn cannot be dropped to bring about an immediate checkmate. Furthermore, in order for pawns, knights and lances to have freedom to move legally, they cannot be dropped on the farthest rank, nor can a knight be placed on the penultimate rank.